1. Field of the Invention
The present invention generally relates to a substrate processing apparatus and a substrate processing method.
2. Description of the Related Art
With the miniaturization of circuit patterns of semiconductor devices, there is a growing demand for techniques for reducing the thickness and improving the uniformity of various films constituting semiconductor devices. In view of such a demand, the so-called molecular layer deposition (MLD) method or the atom layer deposition (ALD) method is known as a film forming method that involves supplying a first reaction gas to a substrate to cause adsorption of the first reaction gas to the surface of the substrate, then supplying a second reaction gas to the substrate to cause a reaction between the first reaction gas that is adsorbed on the surface of the substrate and the second reaction gas, and depositing a film that is made of the reaction product on the substrate (e.g., see Japanese Laid-Open Patent Publication No. 2010-56470).
According to the above film forming method, the reaction gas may be adsorbed to the surface of the substrate in a (quasi) self-saturating manner such that high film thickness controllability, desirable uniformity, and desirable embedding characteristics may be achieved.
However, in view of the miniaturization of circuit patterns, for example, as the aspect ratio of a space in a line/space pattern increases in a trench element separation structure, it becomes increasingly difficult to embed a film in a trench or a space even when the MLD method or the ALD method is used.
For example, when embedding a space having a width of about 30 nm in a silicon oxide film, it may be difficult to introduce a reaction gas to the bottom of such a narrow space, and as a result, the film thickness at the upper end portions of line side walls defining the space may increase. Thus, in some cases, a void may be created in the silicon oxide film having a space embedded by a film. When such a silicon oxide film is etched in a subsequent etching process, for example, an opening communicating with the void may be formed at the upper surface of the silicon oxide film. In such case, an etching gas (or etching solution) may enter the void through the opening to cause contamination, or a metal may enter the void during a metallization process performed thereafter to create defects, for example.
The occurrence of such a problem is not limited to the case of using the MLD method or the ALD method, but may also occur in the case of using a chemical vapor deposition (CVD) method. For example, when embedding a film made of conductive material in a contact hole that is formed in a semiconductor substrate to create a conductive contact hole (a so-called plug), a void may be formed in the plug. In this respect, a method of forming a conductive contact hole while preventing the formation of such a void in the conductive contact hole is known. For example, when embedding a conductive material in a contact hole to form a conductive contact hole, an etch back process may be repeatedly performed to remove an overhanging portion of the conductive material that is formed around the upper end of the contact hole (e.g., see Japanese Laid-Open Patent Publication No. 2003-142484).
However, according to the method described in Japanese Laid-Open Patent Publication No. 2003-142484, the process of forming the conductive material film and the etch back process have to be performed in different apparatuses. Thus, time is required in transporting the substrate back and forth between the apparatuses and stabilizing process conditions in each apparatus such that throughput cannot be increased.
Also, a film forming apparatus and a film forming method are known that may solve the above problems of the method described in Japanese Laid-Open Patent Publication No. 2003-142484. The film forming apparatus and the film forming method enable embedding at a high throughput while reducing the occurrence of voids in a concave pattern formed on the surface of a substrate. The film forming apparatus includes a rotary table on which a substrate is mounted, first and second gas supply units that are capable of supplying first and second reaction gases for film formation to a substrate mounting surface of the rotary table, and an activated gas supply unit that activates and supplies a modification gas for modifying a reaction product generated by a reaction between the first and second reaction gases and an etching gas used for etching. The film formation method involves using such a film forming apparatus to successively repeat the processes of film formation, modification, and etching within the same processing chamber through rotation of the rotary table (e.g., see Japanese Laid-Open Patent Publication No. 2012-209394).
However, in the film forming method described in Japanese Laid-Open Patent Publication No. 2012-209394, the etching amount distribution in the substrate surface cannot be adequately controlled, and it is difficult to achieve etching uniformity in the substrate surface.